But then, they are usually easily repaired and work stable.
There's certainly a lot to be said for the benefits of stable operation. In my youth I used to repair lots of ham/CB gear and it isn't always easy to get a stable reading from some makes/models of counter when probing a low level signal inside a radio. Back in those days I had access to many models of counter and the best of the lot was my old Marconi TF2430 which probably dates back the the early 1970s. It isn't a reciprocal counter but this is to its advantage in terms of radio servicing IMO.
Like your 6667 it only has a 7 digit display but it gives the most stable display of any counter I have ever used. This is all the more remarkable for it having no user controls for input level or triggering/filtering.
I still have it here today and there is no other counter on the planet I would rather use if I had to align a typical CB/HF ham radio today. Brilliant, clear LED display, very little drift in the standard oscillator and a really simple user interface. They need to be treated with some sympathy however as the thermal management of these counters is poor. So it has to be placed somewhere cool and also propped up to allow the lower vents to breathe. Otherwise the regulator at the back gets very hot and this is a common point of failure.
The standard oscillator inside is also much better than the one in my Philips PM6669. Much less drift during warmup and much more stable once warm. It could normally be used straight away as long as the room temperature was 'comfy' as it was rarely more than 7Hz away from 10MHz and usually got within 1-2Hz after a short warmup.
The only user controls on it are the three pushbuttons for gate time/resolution.
i.e. 10Hz or 1Hz or 0.1Hz resolution can be preset. It can display to 10Hz several times a second or to 1Hz in 1 second or to 0.1Hz in 10 seconds. Obviously, it often overflows the display when this happens but it still displays the lower 7 digits and it can do this up to 150MHz (despite only being branded as an 80MHz counter)